Variable reactance coil adapter for induction heating apparatus



Feb; 24, 1970 P. N.-LAVINS 3,497,657

VARIABLE REACTANGE COIL ADAPTER FOR INDUCTION HEATING APPARATUS Filed Dec. 4, 1967 2 Sheets-Sheet 1 INVENTOR.

Q PAUL N. LAVINS ZZ FIG?) BY #wkq/k/zwf dw ATTORNEYS P. N. LAVINS Feb. 24, 1970 vARIABLE REACTANCE COIL ADAPTER FOR INDUCTION HEATING APPARATUS Filed Dec. 4, 196'? 2 Sheets-Sheet 2 ,4 FIG'8 INVENTOR. PAUL N.LAVINS 4M, ATTORNEYS.

United States Patent US. Cl. 21910.75 Claims ABSTRACT OF THE DISCLOSURE A variable reactance coil adapter to electrically con nect a work-coil for the induction heating of workpieces to the secondary winding of a transformer which is connected to the output of a high-frequency generator so as to enable the tuned adjustment of the impedance re fiected from the load to provide correct loading between the power source and the coil.

BACKGROUND OF THE INVENTION Field of the invention This invention pertains to the art of induction heating and more particularly to variable reactance adjustable adapters for a detachable work coil for induction heating.

Description of the prior art Heretofore coils which are utilized with adapter blocks, that allow for controlling the loading on the high-fre quency generator and the power delivered to the work, have been of the type using a common cooling system for the adapter and the coil. It is thus not possible to readily change the work coils so that they may be shaped depending on the configuration of the work piece and the heating pattern required.

A further disadvantage of the prior art controlled inductor blocks is that they have objectionable resistance introduced at the adjustment contact areas which has an adverse efiect on the efliciency of the induction heating. It has been stated in this regard that the conductivity of the conductor for induction heating coils must be at least ninetypercent or better, alfording a continuous passage of electrical current. Examples of prior art patents displaying the above indicated deficiencies are US. Patent No. 2,528,714 issued Nov. 7, 1950 to J. B. Wadham and U8. Patent No. 2,647,200 issued July 28, 1953 to J. A. Redmond.

Summary In accordance with the present invention there is provided an adjustable adapter having an independent fluid circulating cooling system for use with plate-like coils or loop coils that do not require artificial cooling as well as with work-coils that have independent cooling or quench ing systems. The adapter has connecting terminals maintained in spaced apart relationship by means of an insulating spacer wherein one of said terminals comprises a pair of spaced symmetrical body members each having a transverse hollow post thereon to provide a pair of parallel tuning extensions. The extensions are joined in electrical contact by means of an adjustable bridge block that also provides a cross over coolant passage between the coolant passages of the posts.

,It is therefore an object of the present invention to provide an adjustable adapter for an induction heating work-coil that has an independent circulating fluid cooling system.

Another object of the invention is to provide an ad justable adapter that allows the ready interchange of work-coils.

A further object of the invention is the provision of an adjustable adaptor for an induction heating system which does not interfere with the etficiency of the circuit by having maximum electrical contact between the ad justable member and the adapter.

Brief description of the drawings FIG. 1 shows a plan view of the adapter of the present invention;

FIG. 2 is a side elevational view of the adapter of FIG. 1;

FIG. 3 is a cross section taken on line 3-3 of FIG. 2;

FIG. 4 is a perspective view of the adapter being used with one form Of an induction working coil.

FIG. 5 is a view, partially in section, of the adjustable clamp portion of the adapter;

FIG. 6 is a cross-sectional view of one of the terminals of FIG. 1 showing the cooling passages therein; FIG. 7 is a detail view of one of the terminal clamps indicated by dashed lines in FIG. 1.

FIG. 8 is a schematic diagram of a welding circuit em bodying the inventive apparatus.

Description of the preferred embodiment As shown in FIG. 1 the composite adapter 20 is assembled from a pair of mating elements, in this particu* lar example a terminal assembly 22 having a continuous plate 29 and a pair of terminal assemblies 24 and 26 united by a bridge block 27, and having a spacer strip 28 of insulating material such as Glastic, for example, interposed therebetween. At the extreme ends of the terminal assembly 22, the continuous plate 29 has increased thickness portions 30 and 31 forming fish-tail type input and work-coil connector poles, respectively.

At opposite ends of the plates 32 and 34 of the terminal assemblies 24 and 26 there are provided increased thickness portions 36 and 37 forming fish-tail type input and work-coil poles, respectively. The poles 30 and 36 cooperate to form coplanar transformer electrical contact surfaces 42 and 44 (FIG. 4) and the poles 31 and 37 cOoperate to provide work-coil electrical contact sur faces 46 and 48.

The pair of side plates 32 and 34 are juxtaposed in contiguity with a space or zone 52 between such that both plates are in the same plane and clamped on the continuous plate 29 by means of clamp members indicated generally by the dashed lines 54 in FIG. 1 and shown in enlarged detail in FIG. 7. Each clamp 54 comprises a pair of similar blocks formed of a suitable insulating material such as Glastic. The blocks are provided with aligned bores 56 for the reception of threaded bolts 58 whereby the blocks 55 can be drawn toward each other. The facing surfaces of each block 55 has cooperating stepped grooves 60 to provide an opening which conforms with the adapter plates. For purposes of clarity, the clamps 54 are not shown in FIGS. 2 and 4.

The terminal assemblies 24 and 26 are mirror images of each other as shown in the disclosed embodiment, the details of one of which are shown in FIG. 6. Each terminal 24 and 26, adjacent their opposed ends, have posts 62 and 64 fixably secured thereto as by welding. The posts are in the shape of tubes having passages or cooling channels 66. The passage 66 is connected to a rectangular cooling tube 70 extending substantially the length of plate 32. As shown in FIG. 6, tube 70 is connected to a supply pipe or nipple 68 which extends into a bore 73 that in turn communicates with tube 70. The tubes are secured to the faces of plates 32 and 34 by suitable means such as welding, brazing, or the like.

The posts 62 and 64 are joined by means of bridge block member, generally indicated at 27 to complete the electrical circuit so current will flow through the workingcoil for heating a piece of work therein. The bridge block 27 has a hole 76 (FIG. for fluid passage and is connected with taps 78 and 80, to permit the cooling fluid to be introduced and discharged. As shown in FIG. 1. the posts 62 and 64 are connected to nipples 82 and 84 which in turn, are joined to flexible hoses 86 and 88 made from rubber or other non-conducting material to their respective taps 78 and 80.

The water circulating system is completed by providing a separated coolant channel for the continuous terminal assembly 22. A rectangular tube 90 extends the full length of the plate 29 as seen in FIG. 3. The terminal assembly 22 is tapped at either end to permit the cooling liquid to be introduced and discharged through inlet and outlet nipple tubes 94 and 96.

The variation in inductance is obtained by means of the selective movement of bridge block 27 which is adjustably mounted on the posts 62 and 64. The block 27 is formed with first and second spaced openings 98 and 100 extending transversely therethrough for the reception of the posts 62 and 64 respectively. First and second slots 102 and 104 extending transversely through the block and communicating, respectively, between said first and second openings 98 and 100 and the periphery of the block are provided to create free flanges or outer flange jaws 106 and 108. The socket head screws 1'10 and 112 are located in aligned threaded bores 114 and 116 in the flanges 106 and 108.

In order to ensure maximum electrical contact between the block 27 and the posts 62 and 64 upon tightening of the screws 100 and -112 the flanges 106 and 108 are provided with circular cut-outs 118 and 120 having the same radius of curvature as the circular openings 98 and 100. In this manner the flanges 106 and 108 are permitted to be sprung inward so that the posts are held in substantially complete circumferential electrical contact by means of the pressure exerted by the screws 110 and 112.

The importance of applicants use of circular tuning post members 62 and 64 having substantially complete 360 peripheral contact with the openings 98 and 100 of bridge block 27 is that the high-frequency current tends to concentrate on the surfaces of the conducting members. Thus, by means of the present construction the conductivity between the posts and the adjustable bridge block is a maximum and does not materially reduce the efliciency of the circuit.

In this way selected portions of the posts 62 and 64 can be short circuited to vary the impedance of the circuit.

With the bridge block 27 in its extreme outward position as indicated in FIG. 1, all the impedance is in the circuit; and with the block at its extreme inner position (indicated by phantomlines) in FIG. 4, the total impedance in the circuit is a minimum and the current and power through the work-coil is at a maximum.

While the invention is not restricted to the method of forming the adapter 10, the present construction lends itself to convenient and inexpensive fabrication by the use of members having standard sections such as the flat plates 29, 32 and 34, the circular tubes 62 and 64, and the rectangular tubes 70 and 90 which can be employed in the instant embodiment.

It will be readily apparent that the resulting structure provides a pair of continuous water cooled paths for the inductor current throughout the full length of each of the adapter terminal assemblies 22, 24 and 26 as shown in FIG. 1. The boss portions 42 and 44 of terminals 30 and 36 are mounted on the existing output terminals of the secondary winding of the output coil of a generator by means of bolts passed through apertures 122 and 124.

The work-coil 126 having a working aperture 128 for receiving a workpiece is connected to the terminals 31 and 37 by means of bolts (not shown) passed through apertures 132 and 134. The relatively large surfaces of the work-coil abutting edge having the split 136 provide a maximum electrical contact area. The work-coil may be 4 provided with internal quenching ducts to supply liquid cooling agent to said coil to quench the workpiece. Applicants separate cooling system for the adapter thus not only allows for ready interchange of work-coils but allows the quenching sequence to remain independent from the constant cooling operation of the adapter.

It should be pointed out that applicant avoids the problem of having the current flow through the adapter create overheating of the brazing alloy used to secure the tubes 62 and 64 to their associated plates 32 and 34 by having these junctures removed from the maximum heat areas at the terminals. Also in this regard by use of plates 29, 32 and 34 of oversize width to extend on both sides of the metal cooling tubes 70 and applicant provides large areas to assist in cooling the adapter and prevent overheating of the brazed or welded junctures.

The impedance adjustable adapter of the present invention' provides not only for an electrically eflicient device that also allows a variety of work-coils to be easily and efficiently used therewith but provides for a convenient and easily accessible means to adjust the impedance of the circuit. It will further be appreciated that the parallel post and bridge block construction allows for the continuous water-cooled flow during adjustment of the bridge block toward and away from the plane of the terminal plate members.

While the adapter of the instant embodiment is formed from copper or copper-base alloys having a high electrical conductivity it is to be understood, however, that the adapter design of the invention is not limited to any particular material and could be constructed from other metals and alloys.

It will thus be seen that by means of applicants variable reactance coil adapter it is possible to vary the re flected impedance from the load by moving the adjustable bridge block on the stubs or posts 62 and 64. In this way applicant is able to extend the range of a variable ratio transformer when contact surfaces 42 and 44 are electrically connected to the secondary of the transformer. Also it is possible to change a fixed ratio isolation transformer to a variable ratio isolation transformer by means of applicants device.

FIG. 8 shows schematically a welding circuit as one type of induction heating coil circuit that can be used with applicants tuned induction heating coil adapter. The work-coil 140 is shown completing the circuit of the secondary winding 142 with the tuner represented at 144. The primary winding 146 is supplied with high frequency electrical power by means of alternator 148 with suitable breaker contacts provided at 150 and 152.

The foregoing description and accompanying drawings are believed to clearly disclose a preferred embodiment of my invention, but it will be understood that this disclosure is merely illustrative and that such changes in the invention may be made as are fairly within the scope and spirit of the following claims:

1. An adaptor for electrically connecting a work-coil for the inductive heating of workpieces to a secondary winding of a transformer comprising, a pair of coextensive first and second electrically conducting terminal members insulated from each other, said first terminal member being divided to provide a pair of sections, each of said sections having a plate disposed in a common plane 'with one edge of each plate adjacent to and spaced from the other edge to form an insulating zone therebetween, means electrically connecting said sections including a separate post secured to each of said plates adjacent said zone and extending transversely from the plane of said plates, a bridge block slidably engaged on and extending between said posts such that said block is adapted to be selectively positioned in varying locations to vary the impedance of the adaptor, and means for artificially cooling said conducting members and said adjustable means to provide a continuous fluid-cooled path for the current throughout the adaptor.

2. The adaptor as defined in claim 1 and wherein the adjustable engagement between said posts and said block is formed by a pair of circular openings in said block such that each opening has a slot communicating with the opening and the periphery of the block.

3. The adaptor as defined in claim 2 wherein each said slotted opening forms an outer flange jaw provided with a bolt operatively connecting each said jaw for opening and closing the same relative to said block.

4. The adaptor as defined in claim 3 wherein said jaws have semi-circular portions removed from the outer edges thereof to permit said jaws to 'be sprung inward.

5. An adaptor for electrically connecting a work-coil for the inductive heating of workpieces to a secondary winding of a transformer comprising, a pair of electrically conducting terminal members insulated from each other, the first terminal member including first and second sections with an insulating zone therebetween, first and second conductive post members extending respectively from said first and second sections of the first terminal member, a conductive bridge block slidably engaged on and extending between said posts in electrically conductive connection therewith and including clamping means adapted to permit selective positioning of said bridge block on said posts and thereby varying the impedance reflected into said transformer when said adaptor is utilized for connecting a work coil thereto.

References Cited UNITED STATES PATENTS 2,528,714 11/1950 Wadhams 2l910.75 2,647,200 7/1953 Redmond 21910.67

JOSEPH V. TRUHE, Primary Examiner L. H. BENDER, Assistant Examiner US. Cl. X.R. 219--10.49, 10.67 

